package com.jeasy.util;

/**
 * 距离计算
 */
public final class DistanceUtils {

    private final static double EARTH_RADIUS = 6378137;
    private static double rad(double d)
    {
        return d * Math.PI / 180.0;
    }

    /**
     * 计算距离（单位：米）
     * @param lat1
     * @param lng1
     * @param lat2
     * @param lng2
     * @return
     */
    public static double getDistance(double lat1, double lng1, double lat2, double lng2)
    {
        double radLat1 = rad(lat1);
        double radLat2 = rad(lat2);
        double a = radLat1 - radLat2;
        double b = rad(lng1) - rad(lng2);

        double s = 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a/2),2) +
                Math.cos(radLat1)*Math.cos(radLat2)*Math.pow(Math.sin(b/2),2)));
        s = s * EARTH_RADIUS;
        s = Math.round(s * 10000) / 10000;
        return s;
    }

    public static void main(String[] args){
        System.out.println(getDistance(43.659362, 120.30606 ,52.438878,143.354836));
        System.out.println(DistanceUtils.getDistance(39.9136110000, 116.3987640000, 39.9138880000, 116.4073880000));
    }
}
